Many of the problems faced by wheelchair users are related to the positioning and ultimate posture of the seated user. Typical problems include progressive spinal deformations such as kyphosis, lordosis, and scoliosis. Poor posture and permanent spinal deformations can cause reduced function and mobility, fatigue, impaired respiration, impaired swallowing, and increased risk of sacreal, coccygeal, lumbar or thoracic tissue break down. Thus, it is very important for any wheelchair seatback system to provide for proper back angle adjustment and support because different users usually require a specifically tailored seat to back angle in order to optimize their own function and mobility.
An advantage of using rigid seatbacks as opposed to sling-type arrangements is that posture control is greatly enhanced. Thus, rigid seatbacks are generally preferred over sling-type seatbacks so that the user may achieve the most appropriate support for a given condition. Moreover, a rigid arrangement increases structural rigidity to the wheelchair, and provides a more effective force transmission element for active wheelchair users.
Another important object to any wheelchair seatback system not using a sling-type arrangement is that it be convenient to remove and install. Disabled users must frequently remove and install the wheelchair back and wheelchair cushion from the wheelchair in order to collapse the wheelchair for storage or transportation, and put it back together for use. This procedure, when performed independently by a user with impaired mobility, is often accomplished from the driver's side seat or passenger's side seat of an automobile. To collapse the wheelchair, the user must first reach out and remove the back. The wheelchair may then be collapsed and be placed in the desired location, such as the rear seat of the automobile. To re-assemble the wheelchair, the user will typically pull the collapsed chair from the rear seat of the car and unfold the chair at ground level next to the car. Once the frame is unfolded, the user must then reach out and attach the seatback onto the wheelchair. Both disassembly and assembly are usually accomplished mostly with one hand because the disabled user must maintain support with the other hand, normally by grasping the steering wheel.
The maneuver of reaching out from the car to attach or detach the wheelchair back can be difficult, particularly since most wheelchair users, especially quadriplegics, have impaired upper extremity function and compromised dexterity in their hands and, therefore, may experience great difficulties in manipulating heavy objects in a precise manner. Because of this, the degree of manipulation required of a particular wheelchair component, such as a seatback, will often determine whether or not it can even be used by a disabled individual.
Besides having the seatback system as simple and easy as possible to attach and detach, it is also beneficial to have it attachable and detachable by a user from in the front of the wheelchair. This is because a user having just transferred out of the wheelchair, or about to transfer into the wheelchair, will usually be positioned generally in front of the wheelchair. Accordingly, a simplified seatback mounting mechanism that enables the wheelchair user to swiftly attach or detach the back system to or from the wheelchair, especially from a position in front of the wheelchair, would greatly expand the usability of the seatback system to the disabled population.
Another problem facing wheelchair back systems has been the variability of each type of commercially available wheelchair. In particular, the vertical upright posts or canes often differ in configuration from one wheelchair to another. The nominal diameter of the posts may vary from ½″ to 1¼″. The center to center distances of the posts may vary ±½″ despite the typical designation by the wheelchair manufacturer that the chair is a nominal width to the nearest inch (i.e., an 18″ wide wheelchair may actually measure 17.6″ wide). These vertical posts may also not be parallel and indeed are designed to taper outward from bottom to top. All of these variations along with the metric size requirements offered by foreign wheelchair manufacturers demand either a custom made seatback system or a custom fit off-the-shelf seatback system with considerable adjustability through the available size ranges of wheelchairs.
Many prior art systems have dealt with the post (cane) dimension variability by maintaining a maximum and minimum width capability, which inherently results in a loose fit at the narrow end of the width limit. The loose fit may cause the seatback to shift from side to side or, in some cases, the outer margins of the seatback system overhang the width of the wheelchair and interfere with armrests and other peripheral features on the wheelchair.
Numerous attempts have been made to replace the conventional wheelchair upholstery sling back with a comfortable, sturdy, adjustable, supportive, pressure relieving, easy to use seatback system. However, prior art systems have generally failed to provide a suitable degree of adjustability, without loss of seat depth, in conjunction with a system that is easily attached or detached from the wheelchair and that is also capable of seatback angle adjustment with no loss of seat depth while the user is occupying the wheelchair. Available systems known to date have also failed to incorporate both the capability to adjust the seatback angle while the user is in the wheelchair and a removably attachable mounting system that does not alter the adjusted seatback angle each time the back system is removed from the wheelchair. Furthermore, the prior art seatback systems have generally failed to address the related problems of maintaining pelvic alignment while the back system is adjusted to the optimum seat to seatback angle.